Interplay of CMB Temperature, Space Curvature, and Expansion Rate Parameters

Understand

The cosmic microwave background (CMB) temperature, $T$, surely the most precisely measured cosmological parameter, has been inferred from {\it local} measurements of the blackbody spectrum to an exquisite precision of 1 part in $\sim 4700$.

• On the other hand, current precision allows inference of other basic cosmological parameters at the $\sim 1\%$ level from CMB power spectra, galaxy correlation and lensing, luminosity distance measurements of supernovae, as well as other cosmological probes.
• A basic consistency check of the standard cosmological model is an independent inference of $T$ at recombination.
• In this work we first use the recent Planck data, supplemented by either the first year data release of the dark energy survey (DES), baryon acoustic oscillations (BAO) data, and the Pantheon SNIa catalog, to extract $T$ at the $\sim 1\%$ precision level.